U.S. patent number 11,165,452 [Application Number 16/716,782] was granted by the patent office on 2021-11-02 for radio frequency switching circuit with hot-switching immunity.
This patent grant is currently assigned to MOTOROLA SOLUTIONS, INC.. The grantee listed for this patent is Motorola Solutions, Inc.. Invention is credited to Mitchell R. Blozinski, Anders Stensgaard Larsen, Daniel Studer.
United States Patent |
11,165,452 |
Larsen , et al. |
November 2, 2021 |
Radio frequency switching circuit with hot-switching immunity
Abstract
Apparatus and methods for providing hot-switching immunity for
radio frequency switching circuits are disclosed. A radio frequency
switching circuit may include both a mechanical switch and a
solid-state switch. The mechanical switch may be configurable to
couple an output path of a power amplifier to a subsequent
component in its transmission path when in a first mechanical
switch state and to decouple the output path of the power amplifier
from the subsequent component when in a second mechanical switch
state. The solid-state switch may be configurable to operatively
decouple the mechanical switch from a radio frequency power source
when in a first solid-state switch state but not when in a second
solid-state switch state. The solid-state switch may be in the
first solid-state switch state during transitions of the mechanical
switch between the first and second mechanical switch states.
Inventors: |
Larsen; Anders Stensgaard
(Hillerod, DK), Blozinski; Mitchell R. (Lake In The
Hills, IL), Studer; Daniel (Hawthorn Woods, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Motorola Solutions, Inc. |
Chicago |
IL |
US |
|
|
Assignee: |
MOTOROLA SOLUTIONS, INC.
(Chicago, IL)
|
Family
ID: |
1000005904592 |
Appl.
No.: |
16/716,782 |
Filed: |
December 17, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20210184709 A1 |
Jun 17, 2021 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03F
3/21 (20130101); H03K 17/56 (20130101); H04B
1/0458 (20130101); H03F 2200/451 (20130101) |
Current International
Class: |
H04B
1/04 (20060101); H03F 3/21 (20060101); H03K
17/56 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kim; Jung
Attorney, Agent or Firm: Baker Botts L.L.P.
Claims
We claim:
1. A radio frequency switching circuit, comprising: a mechanical
switch configured to operatively couple an output path of a power
amplifier in a first transmission path to a subsequent component in
the first transmission path when in a first mechanical switch state
and to operatively decouple the output path of the power amplifier
from the subsequent component in the first transmission path when
in a second mechanical switch state, wherein: the mechanical switch
is positioned in a second transmission path parallel to the first
transmission path; the mechanical switch is in an open position
when in the first mechanical switch state; the mechanical switch is
in a closed position when in the second mechanical switch state;
and a solid-state switch configured to operatively decouple the
mechanical switch from a radio frequency power source in the first
transmission path when in a first solid-state switch state and not
decouple the mechanical switch from the radio frequency power
source in the first transmission path when in a second solid-state
switch state, wherein the solid-state switch is configured to be in
the first solid-state switch state during transitions of the
mechanical switch from the first mechanical switch state to the
second mechanical switch state and from the second mechanical
switch state to the first mechanical switch state.
2. The radio frequency switching circuit of claim 1, wherein: to
operatively decouple the mechanical switch from the radio frequency
power source in the first transmission path when in the first
solid-state switch state, the solid-state switch is configured to
impart a first impedance lower than a second impedance at a pin of
the mechanical switch; and the solid-state switch is configured to
impart the second impedance higher than the first impedance at the
pin of the mechanical switch when in the second solid-state switch
state.
3. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is configured to be in the second solid-state
switch state while the mechanical switch is in the first mechanical
switch state; and the solid-state switch is configured to be in the
second solid-state switch state while the mechanical switch is in
the second mechanical switch state.
4. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is configured to be in the first solid-state
switch state while the mechanical switch is in the first mechanical
switch state; and the solid-state switch is configured to be in the
second solid-state switch state while the mechanical switch is in
the second mechanical switch state.
5. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is configured to be in the first solid-state
switch state while the mechanical switch is in the second
mechanical switch state; and the solid-state switch is configured
to be in the second solid-state switch state while the mechanical
switch is in the first mechanical switch state.
6. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is configured to be in the first solid-state
switch state while the mechanical switch is in the first mechanical
switch state; and the solid-state switch is configured to be in the
first solid-state switch state while the mechanical switch is in
the second mechanical switch state.
7. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is in a closed circuit state when in the first
solid-state switch state; and the solid-state switch is in an open
circuit state when in the second solid-state switch state.
8. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is in an open circuit state when in the first
solid-state switch state; and the solid-state switch is in a closed
circuit state when in the second solid-state switch state.
9. The radio frequency switching circuit of claim 1, wherein the
respective positions of the mechanical switch when in the first
mechanical switch state and when in the second mechanical switch
state are dependent on the length of a third transmission path
between a point at which the output path of the power amplifier is
decoupled from the subsequent component and the mechanical
switch.
10. The radio frequency switching circuit of claim 1, wherein the
respective open circuit or closed circuit states of the solid-state
switch when in the first solid-state switch state and when in the
second solid-state switch state are dependent on the length of a
third transmission path between the solid-state switch and a point
at which the mechanical switch is operatively decoupled from the
radio frequency power source in the first transmission path when
the solid-state switch is in the first solid-state switch
state.
11. The radio frequency switching circuit of claim 1, wherein: the
mechanical switch is positioned in a second transmission path
parallel to the first transmission path; and the solid-state switch
is positioned in a third transmission path parallel to the second
transmission path.
12. The radio frequency switching circuit of claim 1, wherein: the
solid-state switch is positioned in a second transmission path
parallel to the first transmission path; and the radio frequency
switching circuit further comprises a substitution switch in a
third transmission path parallel to the second transmission path,
the substitution switch configured to operatively decouple the
output path of the power amplifier from the subsequent component
while no electrical power is supplied to the solid-state
switch.
13. The radio frequency switching circuit of claim 12, wherein: the
substitution switch comprises an additional mechanical switch whose
position when configured to operatively decouple the output path of
the power amplifier from the subsequent component is dependent on
the length of the third transmission path.
14. The radio frequency switching circuit of claim 1, wherein: the
mechanical switch is positioned in series with the output path of
the power amplifier in the first transmission path; and the
solid-state switch is positioned in a second transmission path
parallel to the first transmission path.
15. The radio frequency switching circuit of claim 1, wherein: the
radio frequency switching circuit further comprises: an
intermediate mechanical switch; a second transmission path between
the output path of the power amplifier and the mechanical switch; a
third transmission path between the output path of the power
amplifier and the solid-state switch; and a fourth transmission
path between the output path of the power amplifier and the
intermediate mechanical switch; the second transmission path is
parallel to the third transmission path and to the fourth
transmission path; to operatively decouple the mechanical switch
from the radio frequency power source in the first transmission
path when in the first solid-state switch state: the solid-state
switch is configured to operatively decouple the intermediate
mechanical switch from the radio frequency power source in the
first transmission path; and the intermediate mechanical switch is
configured to operatively decouple the mechanical switch from the
radio frequency power source in the first transmission path.
16. An electronic communication device, comprising: a first power
amplifier; and a first radio frequency switching circuit,
comprising: a first mechanical switch configured to operatively
couple an output path of the first power amplifier in a first
transmission path to an antenna when in a first mechanical switch
state and to operatively decouple the output path of the first
power amplifier from the antenna when in a second mechanical switch
state, wherein: the first mechanical switch is positioned in a
second transmission path parallel to the first transmission path;
the first mechanical switch is in an open position when in the
first mechanical switch state; the first mechanical switch is in a
closed position when in the second mechanical switch state; and a
first solid-state switch configured to operatively decouple the
first mechanical switch from a radio frequency power source in the
first transmission path when in a first solid-state switch state
and not decouple the first mechanical switch from the radio
frequency power source in the first transmission path when in a
second solid-state switch state, wherein the first solid-state
switch is configured to be in the first solid-state switch state
during transitions of the first mechanical switch from the first
mechanical switch state to the second mechanical switch state and
from the second mechanical switch state to the first mechanical
switch state.
17. The electronic communication device of claim 16, wherein: to
operatively decouple the first mechanical switch from the radio
frequency power source in the first transmission path when in the
first solid-state switch state, the first solid-state switch is
configured to impart a first impedance lower than a second
impedance at a pin of the first mechanical switch; and the first
solid-state switch is configured to impart the second impedance
higher than the first impedance at the pin of the first mechanical
switch when in a second solid-state switch state.
18. The electronic communication device of claim 16, wherein the
respective solid-state switch states in which the first solid-state
switch is configured and the respective open circuit or closed
circuit states of the first solid-state switch while the first
mechanical switch is in the first mechanical switch state and while
the first mechanical switch is in the second mechanical switch
state are dependent on the length of a third transmission path
between the first solid-state switch and a point at which the first
mechanical switch is operatively decoupled from the radio frequency
power source in the first transmission path when the first
solid-state switch is in the first solid-state switch state.
19. The electronic communication device of claim 16, wherein the
respective positions of the first mechanical switch when in the
first mechanical switch state and when in the second mechanical
switch state are dependent on the length of a third transmission
path between a point at which the output path of the first power
amplifier is decoupled from the antenna and the first mechanical
switch.
20. The electronic communication device of claim 16, wherein: the
first solid-state switch is positioned in a second transmission
path parallel to the first transmission path; and the radio
frequency switching circuit further comprises a substitution switch
in a third transmission path parallel to the second transmission
path, the substitution switch configured to operatively decouple
the output path of the first power amplifier from the antenna while
no electrical power is supplied to the first solid-state switch,
wherein the substitution switch comprises an additional mechanical
switch whose position when configured to operatively decouple the
output path of the first power amplifier from the antenna is
dependent on the length of the third transmission path.
21. The electronic communication device of claim 16, further
comprising: a second power amplifier; and a second radio frequency
switching circuit, comprising: a second mechanical switch
configured to operatively couple an output path of the second power
amplifier in a second transmission path to an antenna when in a
third mechanical switch state and to operatively decouple the
output path of the second power amplifier from the antenna when in
a fourth mechanical switch state; and a second solid-state switch
configured to operatively decouple the second mechanical switch
from a radio frequency power source in the second transmission path
when in a third solid-state switch state and not decouple the
second mechanical switch from the radio frequency power source in
the second transmission path when in a fourth solid-state switch
state, wherein the second solid-state switch is configured to be in
the third solid-state switch state during transitions of the second
mechanical switch from the third mechanical switch state to the
fourth mechanical switch state and from the fourth mechanical
switch state to the third mechanical switch state.
22. A radio frequency switching circuit, comprising: a mechanical
switch configured to operatively couple an output path of a power
amplifier in a first transmission path to a subsequent component in
the first transmission path when in a first mechanical switch state
and to operatively decouple the output path of the power amplifier
from the subsequent component in the first transmission path when
in a second mechanical switch state, wherein the mechanical switch
is in an open position when in the first mechanical switch state
and wherein the mechanical switch is in a closed position when in
the second mechanical switch state; and a solid-state switch
configured to operatively decouple the mechanical switch from a
radio frequency power source in the first transmission path when in
a first solid-state switch state and not decouple the mechanical
switch from the radio frequency power source in the first
transmission path when in a second solid-state switch state,
wherein the solid-state switch is configured to be in the first
solid-state switch state during transitions of the mechanical
switch from the first mechanical switch state to the second
mechanical switch state and from the second mechanical switch state
to the first mechanical switch state.
Description
BACKGROUND OF THE INVENTION
Radio Frequency (RF) communication systems pervade the modern
world, connecting an ever-growing array of devices and services for
a variety of consumer, industrial, and defense applications. The
proliferation of legacy and new RF communication standards, along
with the adoption of frequency and modulation-agile Software
Defined Radio (SDR) technology, allows communications systems to
support a broad frequency range and modulation library, even on
commodity level hardware. For certain communications system and
devices, there may be a requirement to support high power
hot-switching, in which radio frequency signal switching is
performed while the system or device is powered on and operating
and, at the same time, very aggressive intermodulation distortion
(IMD) performance requirements.
Existing high power RF switching circuits are susceptible to
hot-switching problems or poor IMD performance. For example, the
repeated hot-switching of a relay can have a major impact on the
life of the relay. Relays that perform hot-switching of signals run
hotter than relays that do not perform hot-switching, and their
contacts erode much faster than the contacts of relays that do not
perform hot-switching. In addition, mechanical relays can be prone
to silicon deposition on the contacts when arcing during
hot-switching in a silicon vapor rich environment. These factors
can cause relays that perform hot-switching to fail faster than
relays that do not perform hot-switching. Solid-state switches,
such as PIN diodes, while capable of supporting hot-switching
without experiencing reliability issues, are not capable of
achieving the low levels of IMD required in many RF
transmitters.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The accompanying figures, where like reference numerals refer to
identical or functionally similar elements throughout the separate
views, together with the detailed description below, are
incorporated in and form part of the specification, and serve to
further illustrate embodiments of concepts that include the claimed
invention, and explain various principles and advantages of those
embodiments.
FIG. 1 is a flow diagram of selected elements of an example method
for operating a radio frequency switching circuit including both a
mechanical switch and a solid-state switch for hot-switching
immunity, in accordance with some embodiments
FIG. 2A is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity and
operating in a power amplifier enabled state, in accordance with a
first embodiment.
FIG. 2B is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity and
operating in a power amplifier disabled state, in accordance with
the first embodiment.
FIG. 3A is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity during a
transition from a power amplifier enabled state to a power
amplifier disabled state, in accordance with the first
embodiment.
FIG. 3B is a timing diagram illustrating the respective states of a
mechanical switch and a solid-state switch in a radio frequency
switching circuit during a transition from a power amplifier
enabled state to a power amplifier disabled state, in accordance
with the first embodiment.
FIG. 4 is a flow diagram of selected elements of an example method
for transitioning a radio frequency switching circuit including
both a mechanical switch and a solid-state switch from a power
amplifier enabled state to a power amplifier disabled state, in
accordance with some embodiments.
FIG. 5A is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity during a
transition from a power amplifier disabled state to a power
amplifier enabled state, in accordance with the first
embodiment.
FIG. 5B is a timing diagram illustrating the respective states of a
mechanical switch and a solid-state switch in a radio frequency
switching circuit during a transition from a power amplifier
disabled state to a power amplifier enabled state, in accordance
with the first embodiment.
FIG. 6 is a flow diagram of selected elements of an example method
for transitioning a radio frequency switching circuit including
both a mechanical switch and a solid-state switch from a power
amplifier disabled state to a power amplifier enabled state, in
accordance with some embodiments.
FIG. 7A is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity and
operating in a power amplifier enabled state, in accordance with a
second embodiment.
FIG. 7B is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including both a mechanical
switch and a solid-state switch for hot-switching immunity and
operating in a power amplifier disabled state, in accordance with
the second embodiment.
FIGS. 8A-8D are circuit diagrams each illustrating selected
elements of a respective radio frequency switching circuit
including both a mechanical switch and a solid-state switch for
hot-switching immunity and operating in a power amplifier enabled
state, in accordance with third, fourth, fifth, and sixth
embodiments.
FIGS. 9A and 9B are circuit diagrams illustrating selected elements
of a radio frequency switching circuit including a mechanical
switch in series with a power amplifier and a solid-state switch
operating in a power amplifier enabled state and in a power
amplifier disabled state, respectively, in accordance with a
seventh embodiment.
FIGS. 10A and 10B are circuit diagrams illustrating selected
elements of a radio frequency switching circuit including a
mechanical switch in series with a power amplifier and a
solid-state switch operating in a power amplifier enabled state and
in a power amplifier disabled state, respectively, in accordance
with an eighth embodiment.
FIGS. 11A and 11B are circuit diagrams illustrating respective
placements of a radio frequency switching circuit including both a
mechanical switch and a solid-state switch for hot-switching
immunity.
FIGS. 12A and 12B are circuit diagrams illustrating selected
elements of a radio frequency switching circuit including a
mechanical switch, a solid-state switch, and a substitution switch
operating in a power amplifier enabled state and in a power
amplifier disabled state, respectively, in accordance with a ninth
embodiment.
FIG. 12C is a circuit diagram illustrating selected elements of a
radio frequency switching circuit including a mechanical switch, a
solid-state switch, and an intermediate mechanical switch, in
accordance with a tenth embodiment.
FIG. 13 is a block diagram illustrating selected elements of a
system including one or more a radio frequency switching circuits,
each including both a mechanical switch and a solid-state switch
for hot-switching immunity, in accordance with some
embodiments.
FIG. 14 is a block diagram illustrating selected elements of a
transmission path in an electronic communication device including
parallel power amplifiers and corresponding parallel radio
frequency switching circuits, each including both a mechanical
switch and a solid-state switch for hot-switching immunity, in
accordance with some embodiments.
Skilled artisans will appreciate that elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements in the figures may be exaggerated relative to other
elements to help to improve understanding of embodiments of the
present invention.
The apparatus and method components have been represented where
appropriate by conventional symbols in the drawings, showing only
those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
DETAILED DESCRIPTION OF THE INVENTION
Disclosed herein are apparatus and methods for providing
hot-switching immunity for radio frequency switching circuits. In
one embodiment, a disclosed radio frequency switching circuit
includes a mechanical switch configured to operatively couple an
output path of a power amplifier in a first transmission path to a
subsequent component in the first transmission path when in a first
mechanical switch state and to operatively decouple the output path
of the power amplifier from the subsequent component in the first
transmission path when in a second mechanical switch state and a
solid-state switch configured to operatively decouple the
mechanical switch from a radio frequency power source in the first
transmission path when in a first solid-state switch state and not
decouple the mechanical switch from the radio frequency power
source in the first transmission path when in a second solid-state
switch state. The solid-state switch is configured to be in the
first solid-state switch state during transitions of the mechanical
switch from the first mechanical switch state to the second
mechanical switch state and from the second mechanical switch state
to the first mechanical switch state.
In at least some embodiments, to operatively decouple the
mechanical switch from the radio frequency power source in the
first transmission path when in the first solid-state switch state,
the solid-state switch may be configured to impart a first
impedance lower than a second impedance at a pin of the mechanical
switch. The solid-state switch may be configured to impart the
second impedance higher than the first impedance at the pin of the
mechanical switch when in the second solid-state switch state.
In various embodiments, the solid-state switch may be configured to
be in the second solid-state switch state while the mechanical
switch is in the first mechanical switch state and the solid-state
switch may be configured to be in the second solid-state switch
state while the mechanical switch is in the second mechanical
switch state. In various embodiments, the solid-state switch may be
configured to be in the first solid-state switch state while the
mechanical switch is in the first mechanical switch state and the
solid-state switch may be configured to be in the second
solid-state switch state while the mechanical switch is in the
second mechanical switch state. In various embodiments, the
solid-state switch may be configured to be in the first solid-state
switch state while the mechanical switch is in the second
mechanical switch state and the solid-state switch may be
configured to be in the second solid-state switch state while the
mechanical switch is in the first mechanical switch state. In
various embodiments, the solid-state switch may be configured to be
in the first solid-state switch state while the mechanical switch
is in the first mechanical switch state and the solid-state switch
may be configured to be in the first solid-state switch state while
the mechanical switch is in the second mechanical switch state.
In various embodiments, the respective positions of the mechanical
switch when in the first mechanical switch state and when in the
second mechanical switch state may be dependent on the length of a
second transmission path between a point at which the output path
of the power amplifier is decoupled from the subsequent component
and the mechanical switch. For example, in some embodiments, the
mechanical switch may be in a closed position when in the first
mechanical switch state and may be in an open position when in the
second mechanical switch state. In other embodiments, the
mechanical switch may be in an open position when in the first
mechanical switch state and may be in a closed position when in the
second mechanical switch state.
In various embodiments, the mechanical switch may be positioned in
a second transmission path parallel to the first transmission path
and the solid-state switch is positioned in a third transmission
path parallel to the second transmission path. In various
embodiments, the solid-state switch may be positioned in a second
transmission path parallel to the first transmission path and the
radio frequency switching circuit may further include a
substitution switch in a third transmission path parallel to the
second transmission path. The substitution switch may be configured
to operatively decouple the output path of the power amplifier from
the subsequent component while no electrical power is supplied to
the solid-state switch. The substitution switch may be or include
an additional mechanical switch whose position when configured to
operatively decouple the output path of the power amplifier from
the subsequent component is dependent on the length of the third
transmission path. In various embodiments, the mechanical switch
may be positioned in series with the output path of the power
amplifier in the first transmission path and the solid-state switch
may be positioned in a second transmission path parallel to the
first transmission path.
In various embodiments, the respective open circuit or closed
circuit states of the solid-state switch when in the first
solid-state switch state and when in the second solid-state switch
state may be dependent on the length of a second transmission path
between the solid-state switch and a point at which the mechanical
switch is operatively decoupled from the radio frequency power
source in the first transmission path when the solid-state switch
is in the first solid-state switch state. For example, in some
embodiments, the solid-state switch may be in a closed circuit
state when in the first solid-state switch state and may be in an
open circuit state when in the second solid-state switch state. In
other embodiments, the solid-state switch may be in an open circuit
state when in the first solid-state switch state and may be in a
closed circuit state when in the second solid-state switch
state.
In some embodiments, the radio frequency switching circuit may
further include an intermediate mechanical switch, a second
transmission path between the output path of the power amplifier
and the mechanical switch, a third transmission path between the
output path of the power amplifier and the solid-state switch, and
a fourth transmission path between the output path of the power
amplifier and the intermediate mechanical switch, the second
transmission path being parallel to the third transmission path and
to the fourth transmission path. To operatively decouple the
mechanical switch from the radio frequency power source in the
first transmission path when in the first solid-state switch state,
the solid-state switch may be configured to impart a first
impedance lower than a second impedance at a pin of the
intermediate mechanical switch, and the intermediate mechanical
switch may be configured to impart a third impedance at a pin of
the mechanical switch lower than a fourth impedance imparted at the
pin of the mechanical switch when the mechanical switch is not
decoupled from the from the radio frequency power source. The
solid-state switch may be further configured to impart the second
impedance higher than the first impedance at the pin of the
intermediate mechanical switch when in the second solid-state
switch state.
In one embodiment, a disclosed method for operating a radio
frequency switching circuit includes configuring a mechanical
switch in the radio frequency switching circuit to be in a first
mechanical switch state in which the mechanical switch operatively
couples an output path of a power amplifier in a first transmission
path to a subsequent component in the first transmission path,
configuring a solid-state switch in the radio frequency switching
circuit to be in a first solid-state switch state in which the
solid-state switch operatively decouples the mechanical switch from
a radio frequency power source in the first transmission path
rather than in a second solid-state switch state in which the
solid-state switch does not decouple the mechanical switch from the
radio frequency power source in the first transmission path, and
subsequent to configuring the solid-state switch to be in the first
solid-state switch state, toggling the state of the mechanical
switch from the first mechanical switch state to a second
mechanical switch state in which the mechanical switch operatively
decouples the output path of the power amplifier from the
subsequent component in the first transmission path.
In at least some embodiments, configuring the solid-state switch to
be in the first solid-state switch state may include configuring
the solid-state switch to impart a first impedance at a pin of the
mechanical switch lower than a second impedance imparted by the
solid-state switch at the pin of the mechanical switch when the
solid-state switch is in the second solid-state switch state.
In various embodiments, the method may further include, prior to
configuring the solid-state switch to be in the first solid-state
switch state, operating the radio frequency switching circuit in a
power amplifier enabled state in which the output path of the power
amplifier is coupled to the subsequent component and the state of
the solid-state switch is dependent on the length of a second
transmission path between the solid-state switch and a point at
which the mechanical switch is operatively decoupled from the radio
frequency power source in the first transmission path when the
solid-state switch is in the first solid-state switch state.
In various embodiments, the method may further include, subsequent
to toggling the state of the mechanical switch from the first
mechanical switch state to the second mechanical switch state,
operating the radio frequency switching circuit in a power
amplifier disabled state in which the output path of the power
amplifier is decoupled from the subsequent component and the state
of the solid-state switch is dependent on the length of a second
transmission path between the solid-state switch and a point at
which the mechanical switch is operatively decoupled from the radio
frequency power source in the first transmission path when the
solid-state switch is in the first solid-state switch state.
In various embodiment, the method may further include, subsequent
to toggling the state of the mechanical switch from the first
mechanical switch state to the second mechanical switch state,
configuring the solid-state switch to be in the first solid-state
switch state and, subsequent to configuring the solid-state switch
to be in the first solid-state switch state, toggling the state of
the mechanical switch from the second mechanical switch state to
the first mechanical switch state.
In various embodiments, the solid-state switch may be positioned in
a second transmission path parallel to the first transmission path
and the method may further include configuring a substitution
switch in a third transmission path parallel to the second
transmission path to operatively decouple the output path of the
power amplifier from the subsequent component while no electrical
power is supplied to the solid-state switch.
In various embodiments, the method may further include configuring
a second transmission path between the output path of the power
amplifier and the mechanical switch to be in parallel with a third
transmission path between the output path of the power amplifier
and an intermediate mechanical switch and in parallel with a fourth
transmission path between the output path of the power amplifier
and the solid-state switch. Operatively decoupling the mechanical
switch from the radio frequency power source in the first
transmission path when in the first solid-state switch state may
include configuring the solid-state switch to impart a first
impedance at a pin of the intermediate mechanical switch lower than
a second impedance imparted by the solid-state switch at the pin of
the intermediate mechanical switch when in the second solid-state
switch state and configuring the intermediate mechanical switch to
impart a third impedance at a pin of the mechanical switch lower
than a fourth impedance imparted at the pin of the mechanical
switch when the mechanical switch is not decoupled from the from
the radio frequency power source by the intermediate mechanical
switch.
In one embodiment, a disclosed electronic communication device
includes a first power amplifier and a first radio frequency
switching circuit. The first radio frequency switching circuit
includes a first mechanical switch configured to operatively couple
an output path of the first power amplifier in a first transmission
path to an antenna when in a first mechanical switch state and to
operatively decouple the output path of the first power amplifier
from the antenna when in a second mechanical switch state and a
first solid-state switch configured to operatively decouple the
first mechanical switch from a radio frequency power source in the
first transmission path when in a first solid-state switch state
and not decouple the first mechanical switch from the radio
frequency power source in the first transmission path when in a
second solid-state switch state. The first solid-state switch is
configured to be in the first solid-state switch state during
transitions of the first mechanical switch from the first
mechanical switch state to the second mechanical switch state and
from the second mechanical switch state to the first mechanical
switch state.
In at least some embodiments, to operatively decouple the first
mechanical switch from the radio frequency power source in the
first transmission path when in the first solid-state switch state,
the first solid-state switch may be configured to impart a first
impedance lower than a second impedance at a pin of the first
mechanical switch. The first solid-state switch may be configured
to impart the second impedance higher than the first impedance at
the pin of the first mechanical switch when in a second solid-state
switch state.
In various embodiments, the respective solid-state switch states in
which the first solid-state switch is configured and the respective
open circuit or closed circuit states of the first solid-state
switch while the first mechanical switch is in the first mechanical
switch state and while the first mechanical switch is in the second
mechanical switch state may be dependent on the length of a second
transmission path between the first solid-state switch and a point
at which the first mechanical switch is operatively decoupled from
the radio frequency power source in the first transmission path
when the first solid-state switch is in the first solid-state
switch state. The respective positions of the first mechanical
switch when in the first mechanical switch state and when in the
second mechanical switch state may be dependent on the length of a
second transmission path between a point at which the output path
of the first power amplifier is decoupled from the antenna and the
first mechanical switch.
In various embodiments, the first solid-state switch may be
positioned in a second transmission path parallel to the first
transmission path and the radio frequency switching circuit may
further include a substitution switch in a third transmission path
parallel to the second transmission path, the substitution switch
configured to operatively decouple the output path of the first
power amplifier from the antenna while no electrical power is
supplied to the first solid-state switch. The substitution switch
may be or include an additional mechanical switch whose position
when configured to operatively decouple the output path of the
first power amplifier from the antenna is dependent on the length
of the third transmission path.
In various embodiments, the electronic communication device may
further include a second power amplifier and a second radio
frequency switching circuit. The second radio frequency switching
circuit may include a second mechanical switch configured to
operatively couple an output path of the second power amplifier in
a second transmission path to an antenna when in a third mechanical
switch state and to operatively decouple the output path of the
second power amplifier from the antenna when in a fourth mechanical
switch state and a second solid-state switch configured to
operatively decouple the second mechanical switch from a radio
frequency power source in the second transmission path when in a
third solid-state switch state and not decouple the second
mechanical switch from the radio frequency power source in the
second transmission path when in a fourth solid-state switch state.
The second solid-state switch may be configured to be in the third
solid-state switch state during transitions of the second
mechanical switch from the third mechanical switch state to the
fourth mechanical switch state and from the fourth mechanical
switch state to the third mechanical switch state.
As previously noted, existing high power RF switching circuits are
susceptible to hot-switching problems or poor IMB performance. In
these circuits, RF switching in the range of 100 W RMS and 1 KW
peak power is traditionally implemented using either solid-state
switches, such as RF PIN diodes, or using mechanical switches, such
as mechanical relays. However, there are advantages and
disadvantages to each of these approaches. For example, a
mechanical relay RF switch operates satisfactorily in both ON and
OFF states but can face problems with arcing during hot-switching
of high power RF signals. It is, therefore, not an optimal solution
in applications in which, due to being cycled between ON and OFF
states for power savings or other reasons, the mechanical relay
will be exposed to many switching operations during the life cycle
of the system or device. A mechanical relay that is designed to
handle high levels of hot-switching is typically very
expensive.
A solid-state switch, such as a PIN diode RF switch, may be better
able to handle high levels of hot-switching, since it does not
experience problems with arcing. However, this RF switching
approach results in both high power dissipation when in the ON
state and poor IMB performance when in the ON or OFF state. In some
cases, the power dissipation when in the ON state can be reduced by
using more PIN diodes in parallel, but this may increase the IMB
problem when in the OFF state since more diodes are producing
distortion.
In various embodiments, apparatus and methods described herein for
providing hot-switching immunity for radio frequency switching
circuits may fulfill both power dissipation requirements when in
the ON state and IMD requirements when in the ON and OFF state. The
low-cost, high power RF switching circuits described herein may use
a mechanical switch, such as a mechanical relay, in conjunction
with a solid-state switch, such as an RF PIN diode, arranged in any
of a variety of suitable topologies and sequenced such that
benefits of each switch can be realized during states of operation
in which the other switch has weakness. For example, the mechanical
switch may reduce thermal stress on the solid-state switch during
steady-state operation and may reduce or eliminate IMD that would
otherwise be caused by the solid-state switch. The solid-state
switch may reduce hot-switching stress on the mechanical switch
during transitions from an open circuit condition to a short
circuit condition or from a short circuit condition to an open
circuit condition. While the solid-state switch may have
significant IMD during transitions of the mechanical switch, this
may not be considered a problem due to the switching time being of
very short duration.
More specifically, each of the RF circuits described herein may
include a mechanical switch that is configurable to impart a high
impedance, or operatively decouple, the output path of a power
amplifier when the RF circuit in a disabled state. Conversely, in
an enabled state, the mechanical switch may be configurable to
operatively couple the output path of the power amplifier to a
subsequent component such as an antenna. Each of the RF circuits
described herein may also include a solid-state switch that is
configurable to attenuate the RF power to the mechanical relay when
in a first solid-state switch state, effectively decoupling the RF
power source from the mechanical relay, but not attenuating the RF
power to the mechanical relay when in a second solid-state switch
state. In various embodiments and at certain times, the RF power
source may be the power amplifier itself, such as if the
solid-state switch state is transitioned during transmission by the
power amplifier. In other embodiments or at other times, the RF
power source may be external to the power amplifier, such as when
the RF switching circuit is operating in a system with a parallel
power amplifier configuration and the power amplifier associated
with the RF switching circuit is dekeyed prior to the transition of
the solid-state switch state. In this case, the RF power to the
mechanical switch may flow from other power amplifiers following
the transition.
In embodiments in which the solid-state switch is connected in
parallel to the mechanical switch, to attenuate the RF power and
operatively decouple the mechanical switch from the RF power
source, the solid-state switch may be configured to impart a low
impedance, effectively a short circuit condition, between the RF
power source in a first transmission path and the mechanical relay,
such as at one or more pins of the mechanical switch. In such
embodiments, the solid-state switch, when configured in the
opposite state, may impart a high impedance, effectively an open
circuit condition, at this same location between the RF power
source in the first transmission path and the mechanical switch and
not decouple the mechanical switch from the RF power source.
Conversely, in embodiments in which the solid-state switch is
connected in series with the mechanical switch, to attenuate the RF
power and operatively decouple the mechanical switch from the RF
power source, the solid-state switch may be configured to impart a
high impedance, effectively an open circuit condition, at one or
more pins of the mechanical switch. In such embodiments, the
solid-state switch, when configured in the opposite state, may
impart a low impedance, effectively a short circuit condition,
between the RF power source in a first transmission path and the
mechanical relay, such as at the pin(s) of the mechanical switch
and not decouple the mechanical switch from the RF power
source.
In at least some embodiments, the mechanical switch may only be
exposed to very low RF power during the switching operation to
transition between states. Because these RF switching circuits are
not susceptible to arcing issues, a relatively low cost, low power
class mechanical switch may be used, rather than a large, high
power, high cost mechanical relay. In addition, the RF switching
circuits described herein may have a much faster switching time
than existing RF switching circuits that rely on high power
mechanical relays due to the shorter switching times of the low
power class mechanical switches. For example, the switching time
for an existing RF switching circuit that includes a high power hot
switch capable relay may, per specification, be on the order of 15
ms. The switching time for an RF switching circuit that includes
lower power class relays, such as those usable in the RF switching
circuits described herein, may, per specification, be on the order
of 5 ms. Typical switching times may be faster than specified and
may vary for switches across a wide range of different power
classes.
As described in more detail below, the RF switching circuits
described herein may, optionally, include a substitution switch
that maintains a high impedance output state even when no
electrical power is supplied to the solid-state switch. In this
case, the substitution switch may operate in place of the
solid-state switch to decouple the PA output, similar to the
primary mechanical switch, since the solid-state switch may require
DC power in order to provide the proper impedance for the
decoupling. The substitution switch may also be used to provide a
high impedance state in response to a hardware failure of the
primary mechanical relay, such as for a failure mode over-ride
mechanism, to reduce the power consumption of the solid-state
switch at times other than during a transition of the primary
mechanical switch, such as for enhanced performance, or at other
times and under other conditions. Note that the usefulness of the
substitution switch may be dependent on the particular topology of
the RF switching circuit. For example, the substitution switch may
only be useful when the transmission path in which the primary
mechanical switch is positioned is parallel to the transmission
path between the PA output and a subsequent component, since a
primary mechanical switch in a series configuration may be
configured to be able to be forced to open without any electrical
power supplied by design.
In embodiments in which the mechanical switch is positioned in
series with the power amplifier in the first transmission path, the
mechanical switch may be capable of directly imparting a high
impedance, effectively an open circuit condition, into the first
transmission path when operating in the second mechanical switch
state, which is the PA disabled state, and may be configured to be
in a closed circuit state when operating in the PA enabled
state.
In embodiments in which the mechanical switch is positioned in a
second transmission path parallel to the first transmission path,
the mechanical switch may be capable of imparting a low impedance,
effectively a short circuit condition, into the first transmission
path when operating in the second mechanical switch state. This
short circuit condition may subsequently be transformed to an open
circuit condition in the first transmission path. In such
embodiments, the respective mechanical switch states when operating
in the PA disabled state and in the PA enabled state may be
dependent on the length of a transmission path between the
mechanical switch and the point at which the output path of the
power amplifier is decoupled from a subsequent component in the
first transmission path by the mechanical switch.
In some embodiments, when the solid-state switch is operating in
the first solid-state switch state, the impedance imparted at the
pin of the mechanical switch is lower than the impedance imparted
when operating in the second solid-state switch state, which may
result in reduced electrical stress, or lower RF power, at the pin
of the mechanical switch when RF energy is present. In some
embodiments, the RF power to which the mechanical switch is exposed
using this technique may be reduced by 20 dB to 30 dB or more. The
lower impedance imparted at the pin of the mechanical switch when
the solid-state switch is in its first switch state may reduce both
voltage and current exposure to the mechanical switch.
Electrical delay elements, such as quarter-wave transmission lines,
can transform low impedances that are effectively short circuits to
high impedances that are effectively open circuits, and vice versa.
Therefore, in some embodiments, the individual states of the
solid-state switch and the mechanical switch for a given
operational state may be controlled by the selection and number of
delay elements included in the transmission path between the first
solid-state switch and a point at which the first mechanical switch
is operatively decoupled from the radio frequency power source and
in the transmission path between the mechanical switch and the
point at which the output path of the power amplifier is decoupled
from a subsequent component in the first transmission path. In
various embodiments, each quarter-wave transmission line may, for
example, have an impedance of 50 ohms, 75 ohms, 100 ohms, or
another amount, depending on system characteristics or to optimize
performance.
Referring now to FIG. 1, there is provided a flow diagram of
selected elements of an example method 100 for operating a radio
frequency switching circuit including both a mechanical switch and
a solid-state switch for hot-switching immunity, in accordance with
some embodiments. In some embodiments, the mechanical switch may be
a mechanical relay and the solid-state switch may be a PIN diode
switch. In other embodiments, the solid-state switch may be or
include another type of solid-state switch, such as a MOSFET, a
bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion, such as between cutoff
and saturation states. In other embodiments, the mechanical switch
may be or include another type of electromechanically actuated
switch having one or more poles, rather than a mechanical
relay.
While a particular order of operations is indicated in FIG. 1 for
illustrative purposes, the timing and ordering of such operations
may vary where appropriate without negating the purpose and
advantages of the examples set forth in detail throughout the
remainder of this disclosure. In various embodiments, some or all
of the operations of method 100 may be controlled by a processing
unit within a base station, a mobile station, or another device
configured to transmit and, in some cases, receive baseband
signals.
In this example embodiment, method 100 begins with block 102 and
continues at block 104 with configuring a mechanical switch in a
radio frequency switching circuit to be in a first mechanical
switch state in which it couples an output path of a power
amplifier (PA) in a first transmission path to a subsequent
component in the first transmission path or to be in a second
mechanical switch state in which it decouples the output path of
the PA from the subsequent component. For example, in some
embodiments, the first transmission path may be a transmission path
between the PA and an antenna. The RF switching circuit also
includes a solid-state switch.
If and when, at 106, it is determined that the state of the
mechanical switch is to be toggled, method 100 continues to 108
where, prior to toggling the state of the mechanical switch, the
solid-state switch in the RF switching circuit is configured to be
in a first solid-state switch state in which it operatively
decouples the mechanical switch from an RF power source in the
first transmission path rather than in a second solid-state switch
state in which it does not decouple the mechanical switch from the
RF power source in the first transmission path. For example, in
some embodiments, to operatively decouple the mechanical switch
from the RF power source, the solid-state switch may be configured
to impart a low impedance at a pin of the mechanical switch rather
than to impart a high impedance at the pin of the mechanical
switch.
At 110, method 100 includes toggling the state of the mechanical
switch state and, if needed, toggling the state of the solid-state
switch. For example, in some embodiments, the state of the
solid-state switch when the mechanical switch is in the first
mechanical switch state and the state of the solid-state switch
when the mechanical switch is in the second mechanical switch state
may be dependent on the state of the mechanical switch. In some
embodiments, the solid-state switch may be configured to be in the
first solid-state switch state while the mechanical switch is in
transition between the first and second mechanical switch states
and to be in the second solid-state switch state while the
mechanical switch is in either the first mechanical switch state or
the second mechanical switch state. In other embodiments, the
solid-state switch may be configured to be in the first solid-state
switch state while the mechanical switch is in transition between
the first and second mechanical switch states and while the
mechanical switch is in one of the first and second mechanical
switch states and to be in the second solid-state switch state
while the mechanical switch is in the other one of the first and
second mechanical switch states. In at least some embodiments, the
state of the solid-state switch may be dependent on the length of a
transmission path between the pin of the mechanical switch and the
solid-state switch.
As illustrated in FIG. 1, in at least some embodiments, some or all
of the operations of method 100 may be repeated one or more times
during operation of the RF switching circuit.
In the circuit diagrams shown in FIGS. 7A-7B, 8A-8D, 9A-9B,
10A-10B, 11A-11B, and 12A-12C and the descriptions thereof that
follow, the mechanical switch and the solid-state switch will have
finite electrical length, and compensation in the circuit
connections, such as in the lengths of the transmission lines
between various circuit components, may be required. For example,
such compensation may include the manipulation of circuit elements
by the addition of one or more quarter-wave (90-degree) lengths of
cabling, as appropriate. References to specific interconnecting
line lengths to or from the switching elements in the figures are
intended to be illustrative and not restrictive. For example,
several of figures illustrate an ideal 90-degree transmission line.
In practice, a 90-degree transmission path may include a cable that
is less than a quarter-wave length with the remaining length being
attributed to various components along the path. Similarly, several
of the figures illustrate an ideal 180-degree transmission line. In
practice, a 180-degree transmission path may include a cable that
is less than two quarter-wave lengths with the remaining length
being attributed to various components along the path Note that,
for a 90-degree transmission line, if one end of the transmission
line is shorted, there will be an open circuit condition at the
other end of the line, and vice versa. The effect of a 90-degree
path may thus be realized by a transmission path including any odd
number of 90-degree segments or by a transmission path whose length
is an odd multiple of 90 degrees. In the descriptions herein, the
terms open circuit and closed circuit, when referring to
impedances, are not intended to be literal, and are terms of art
used to refer to very high and very low impedances
respectively.
FIG. 2A is a circuit diagram illustrating selected elements of a
radio frequency (RF) switching circuit 200 including a mechanical
switch and a solid-state switch for hot-switching immunity and
operating in a power amplifier enabled state, in accordance with a
first embodiment. In the illustrated embodiment, the mechanical
switch 220 is a mechanical relay that serves as the primary
switching control for RF switching circuit 200. In the illustrated
embodiment, the solid-state switch 230 is a PIN diode switch that
is ON, and thereby shorted, during both the PA enabled state and
the PA disabled state resulting in an open circuit condition at the
point at which the output path of the power amplifier 202 is
coupled or decoupled from a subsequent component by the mechanical
switch. In other embodiments, the solid-state switch 230 in RF
switching circuit 200 may be or include another type of solid-state
switch, such as a MOSFET, a bipolar junction transistor (BJT), or
another type of transistor that can be operated in a switched
fashion. In other embodiments, the mechanical switch 220 may be or
include another type of electromechanically actuated switch having
one or more poles, rather than a mechanical relay.
The RF switching circuit 200 couples power amplifier 202 to a
subsequent component in a transmission path that includes power
amplifier 202 when operating in the power amplifier enabled state
and decouples power amplifier 202 from the subsequent component
when operating in the power amplifier disabled state. For example,
mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. The solid-state
switch 230 is configured to impart a low impedance at a pin of the
mechanical switch 220, shown as decoupling point 250, to
operatively decouple the mechanical switch 220 from an RF power
source when in a first solid-state switch state and to impart a
higher impedance at the pin of the mechanical switch when in a
second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 208 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220, and
transmission cable 210 represents an ideal 90-degree transmission
line in a third transmission path between power amplifier 202 and
solid-state switch 230.
In the illustrated embodiment, the solid-state switch 230 is
configured to be in the second solid-state switch state while the
mechanical switch 220 is in the first mechanical switch state and
while the mechanical switch 220 is in the second mechanical switch
state. In the illustrated embodiment, the mechanical switch 220 is
in a closed position when in the first mechanical switch state and
is in an open position when in the second mechanical switch state.
In the illustrated embodiment, the solid-state switch 230 is in an
open circuit state when in the first solid-state switch state and
is in a closed circuit state when in the second solid-state switch
state. In the illustrated embodiment, the mechanical switch 220 is
positioned in the second transmission path parallel to the first
transmission path and the solid-state switch 230 is positioned in
the third transmission path parallel to the second transmission
path.
In FIG. 2A, the radio frequency switching circuit 200 is operating
in a power amplifier enabled state. In this example, the mechanical
switch is in the first mechanical switch state and the solid-state
switch is in the second solid-state switch state. In this PA
enabled state, PA 202 delivers power to RF PA OUT 225 and any
subsequent component(s) in the transmission path.
FIG. 2B is a circuit diagram illustrating selected elements of
radio frequency switching circuit 200 when operating in a power
amplifier disabled state, in accordance with the first embodiment.
In this example, the mechanical switch is in the second mechanical
switch state and the solid-state switch is in the second
solid-state switch state. In this PA disabled state, the power
amplifier is decoupled from PA RF OUT 225.
FIG. 3A is a circuit diagram illustrating selected elements of
radio frequency switching circuit 200 during a transition from a
power amplifier enabled state to a power amplifier disabled state,
in accordance with the first embodiment. In the illustrated
embodiment, the solid-state switch 230 is a PIN diode switch that
is OFF, and thereby open, during a transition from the PA enabled
state to the PA disabled state resulting in a short circuit
condition at the point at which the output path of the power
amplifier 202 is coupled or decoupled from the mechanical switch,
shown as decoupling point 250. In at least some embodiments, this
will minimize the RF power at the mechanical switch, thereby
reducing or eliminating the effects of high power
hot-switching.
FIG. 3B is a timing diagram 350 illustrating the respective states
of a mechanical switch and a solid-state switch in a radio
frequency switching circuit during a transition from a power
amplifier enabled state to a power amplifier disabled state, in
accordance with the first embodiment. As illustrated in timing
diagram 350, the sequencing of the switch states may be as follows:
in response to a change in a PA enable control signal 356
indicating that the state of the RF switching circuit is to be
changed from the power amplifier enabled state (ON) to the power
amplifier disabled state (OFF) at time 351, and prior to toggling
the state of a control signal for the mechanical switch, shown as
main relay control 354, the state of a control signal for the
solid-state switch, shown as PIN control 352, is toggled from its
low impedance state (ON) to its high impedance state (OFF) at time
353.
In this example, while the solid-state switch is in its high
impedance state (OFF), where a low impedance is thereby imparted at
the pin of the mechanical relay, the main relay control 354 is
toggled from the PA enabled state (ON) to the PA disabled state
(OFF) at time 355. In this example, due to the topology of the RF
switching circuit and the lengths of various transmission paths in
the RF switching circuit, once the RF switching circuit is in the
PA disabled state (OFF), the solid-state switch is returned to its
low impedance state (ON) at time 357, where it presents a high
impedance to the pin of the mechanical relay. In other embodiments,
due again to the topology of the RF switching circuit and the
lengths of various transmission paths in the RF switching circuit,
the solid-state switch might remain in the high impedance state
(OFF) while the RF switching circuit is in the PA disabled state.
In one example embodiment, the period during which the solid-state
switch is in the high impedance state (OFF) may be on the order of
10 milliseconds or less, depending on the switching time of the
mechanical switch and the solid-state switch.
Referring now to FIG. 4, there is provided a flow diagram of
selected elements of an example method 400 for transitioning a
radio frequency switching circuit including a mechanical switch and
a solid-state switch from a power amplifier enabled state to a
power amplifier disabled state, in accordance with some
embodiments. While a particular order of operations is indicated in
FIG. 4 for illustrative purposes, the timing and ordering of such
operations may vary where appropriate without negating the purpose
and advantages of the examples set forth in detail throughout the
remainder of this disclosure. In various embodiments, some or all
of the operations of method 400 may be controlled by a processing
unit within a base station, a mobile station, or another device
configured to transmit and, in some cases, receive baseband
signals.
In this example embodiment, method 400 begins with block 402 and
continues at block 404 with configuring a radio frequency (RF)
switching circuit such that when a mechanical switch in the circuit
is in a first mechanical switch state and electrical power is
supplied, the mechanical switch will couple an output path of a
power amplifier (PA) in a first transmission path to a subsequent
component in the first transmission path, and such that a
substitution switch will decouple the output path of the PA from
the subsequent component in the event that no electrical power is
supplied to the solid-state switch. For example, in some
embodiments, the first transmission path may be a transmission path
between the PA and an antenna. In other embodiments, the RF
switching circuit might not include a substitution switch.
At 406, the method includes operating the RF switching circuit in a
PA enabled state in which the output path of the PA is coupled to
the subsequent component and the state of a solid-state switch in
the RF circuit is dependent on the length of a second transmission
path between the solid-state switch and a decoupling point between
the mechanical switch and an RF power source in the first
transmission path.
At 408, prior to toggling the state of the mechanical switch, the
method includes configuring the solid-state switch to be in a first
solid-state switch state in which it decouples the mechanical
switch from an RF power source in the first transmission path.
At 410, method 400 includes toggling the mechanical switch state
from the first mechanical switch state to a second mechanical
switch state in which it decouples the PA output path from the
subsequent component.
At 412, the method includes operating the RF switching circuit in a
PA disabled state in which the output path of the PA is decoupled
from the subsequent component and the state of the solid-state
switch is dependent on the length of the second transmission
path.
In some embodiments, the mechanical switch may be a mechanical
relay and the solid-state switch may be a PIN diode switch. In
other embodiments, the solid-state switch may be or include another
type of solid-state switch, such as a MOSFET, a bipolar junction
transistor (BJT), or another type of transistor that can be
operated in a switched fashion. In other embodiments, the
mechanical switch may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
In at least some embodiments, some or all of the operations of
method 400 illustrated in FIG. 4 may be repeated one or more times
during operation of the RF switching circuit.
FIG. 5A is a circuit diagram illustrating selected elements of
radio frequency switching circuit 200 during a transition from a
power amplifier disabled state to a power amplifier enabled state,
in accordance with the first embodiment. In the illustrated
embodiment, the solid-state switch 230 is a PIN diode switch that
is OFF, and thereby open, during a transition from the PA disabled
state to the PA disabled state resulting in a short circuit
condition at the point at which the output path of the power
amplifier 202 is coupled or decoupled from the mechanical switch,
shown as decoupling point 250.
FIG. 5B is a timing diagram 550 illustrating the respective states
of a mechanical switch and a solid-state switch in a radio
frequency switching circuit during a transition from a power
amplifier disabled state to a power amplifier enabled state, in
accordance with the first embodiment. As illustrated in timing
diagram 550, the sequencing of the switch states may be as follows:
prior to toggling the state of a control signal for the mechanical
switch, shown as main relay control 354, the state of a control
signal for the solid-state switch, shown as PIN control 352, is
toggled from a low impedance state (ON) to a high impedance state
(OFF) at time 361.
In this example, while the solid-state switch is in the high
impedance state, the main relay control 354 is toggled from the PA
disabled state (OFF) to the PA enabled state (ON) at time 362. In
this example, due to the topology of the RF switching circuit and
the lengths of various transmission paths in the RF switching
circuit, once the RF switching circuit is in the PA enabled state
(OFF), the solid-state switch is returned to the low impedance
state (ON) at time 363 and the PA enable control signal 356 is
changed from the power amplifier disabled state (OFF) to the power
amplifier enabled state (ON) at time 364, indicating that the state
of the RF switching circuit has changed to the power amplifier
enabled state. In other embodiments, due again to the topology of
the RF switching circuit and the lengths of various transmission
paths in the RF switching circuit, the solid-state switch might
remain in the high impedance state (OFF) while the RF switching
circuit is in the PA enabled state. In one example embodiment, the
period during which the solid-state switch is in the high impedance
state (OFF) may be on the order of 10 milliseconds or less,
depending on the switching time of the mechanical switch and the
solid-state switch.
Referring now to FIG. 6, there is provided a flow diagram of
selected elements of an example method 600 for transitioning a
radio frequency switching circuit including a mechanical switch and
a solid-state switch from a power amplifier disabled state to a
power amplifier enabled state, in accordance with some embodiments.
While a particular order of operations is indicated in FIG. 6 for
illustrative purposes, the timing and ordering of such operations
may vary where appropriate without negating the purpose and
advantages of the examples set forth in detail throughout the
remainder of this disclosure. In various embodiments, some or all
of the operations of method 600 may be controlled by a processing
unit within a base station, a mobile station, or another device
configured to transmit and, in some cases, receive baseband
signals.
In this example embodiment, method 600 begins with block 602 and
continues at block 604 with configuring a radio frequency (RF)
switching circuit such that when a mechanical switch in the circuit
is in a first mechanical switch state and electrical power is
supplied, the mechanical switch will decouple an output path of a
power amplifier (PA) in a first transmission path from a subsequent
component in the first transmission path, and such that a
substitution switch will decouple the output path of the PA from
the subsequent component in the event that no electrical power is
supplied to the solid-state switch. For example, in some
embodiments, the first transmission path may be a transmission path
between the PA and an antenna. In other embodiments, the RF
switching circuit might not include a substitution switch.
At 606, the method includes operating the RF switching circuit in a
PA disabled state in which the output path of the PA is decoupled
from the subsequent component and the state of a solid-state switch
in the RF circuit is dependent on the length of a second
transmission path between the solid-state switch and a decoupling
point between the mechanical switch and an RF power source in the
first transmission path.
As described below in reference to FIGS. 12A and 12B, while
electrical power is supplied to the solid-state switch, the state
of the substitution switch may have no effect on the operation of
the RF switching circuit.
At 608, prior to toggling the state of the mechanical switch,
method 600 includes configuring the solid-state switch to be in a
first solid-state switch state in which it decouples the mechanical
switch from an RF power source in the first transmission path.
At 610, the method includes toggling the mechanical switch state
from the first mechanical switch state to a second mechanical
switch state in which it couples the PA output path to the
subsequent component.
At 612, the method includes operating the RF switching circuit in a
PA enabled state in which the output path of the PA is coupled to
the subsequent component and the state of the solid-state switch is
dependent on the length of the second transmission path.
In some embodiments, the mechanical switch may be a mechanical
relay and the solid-state switch may be a PIN diode switch. In
other embodiments, the solid-state switch may be or include another
type of solid-state switch, such as a MOSFET, a bipolar junction
transistor (BJT), or another type of transistor that can be
operated in a switched fashion. In other embodiments, the
mechanical switch may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
In at least some embodiments, some or all of the operations of
method 600 illustrated in FIG. 6 may be repeated one or more times
during operation of the RF switching circuit.
While a particular embodiment is illustrated in FIGS. 2A-2B, 3A,
and 5A and described in detail above, the techniques described
herein for using an RF switching circuit having both a mechanical
switch and a solid-state switch to provide hot-switching immunity
and other advantages may be implemented using RF switching circuits
with topologies other than those illustrated in FIGS. 2A-2B, 3A,
and 5A. For example, in various embodiments, the mechanical switch
and the solid-state switch may be positioned in series or in
parallel with each other or with other elements of the RF switching
circuit. Similarly, the particular states of the mechanical switch,
the solid-state switch and the overall state of the RF switching
circuit may be dependent on the lengths of various transmission
paths between these and other elements of the RF switching circuit.
In some cases, with different topologies, there may be certain
performance trade-offs such as differences in insertion loss,
intermodulation distortion, component cost, or power handling
capability, for example. RF switching circuits with other
topologies are illustrated in FIGS. 7A-7B, 8A-8D, 9A-9B, 10A-10B,
11A-11B, and 12A-12C, in accordance with different embodiments.
FIG. 7A is a circuit diagram illustrating selected elements of a
radio frequency switching circuit 700 including a mechanical switch
and a solid-state switch for hot-switching immunity and operating
in a power amplifier enabled state, in accordance with a second
embodiment. In this PA enabled state, PA 202 delivers power to RF
PA OUT 225 and any subsequent component(s) in the transmission
path. In the illustrated embodiment, the mechanical switch 220 is a
mechanical relay that serves as the primary switching control for
RF switching circuit 200 and the solid-state switch 230 is a PIN
diode switch. In other embodiments, the solid-state switch 230 may
be or include another type of solid-state switch, such as a MOSFET,
a bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion. In other embodiments,
the mechanical switch 220 may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
The RF switching circuit 700 couples power amplifier 202 to a
subsequent component in a transmission path that includes power
amplifier 202 when operating in the power amplifier enabled state
and decouples power amplifier 202 from the subsequent component
when operating in the power amplifier disabled state. For example,
mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. The solid-state
switch 230 is configured to impart a low impedance at a pin of the
mechanical switch 220, shown as decoupling point 250, to
operatively decouple the mechanical switch 220 from an RF power
source when in a first solid-state switch state and to impart a
higher impedance at the pin of the mechanical switch when in a
second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 714 represents an
ideal 180-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220, and
transmission cable 210 represents an ideal 90-degree transmission
line in a third transmission path between power amplifier 202 and
solid-state switch 230. In practice, a 180-degree transmission path
may include a cable that is less than a half wave length with the
remaining length being attributed to various components along the
path. In addition, the effect of a 180-degree path may be realized
by a transmission path including any even number of 90-degree
segments or by a transmission path whose length is an even multiple
of 90 degrees.
In the illustrated embodiment, the solid-state switch 230 is
configured to be in the second solid-state switch state while the
mechanical switch 220 is in the first mechanical switch state and
while the mechanical switch 220 is in the second mechanical switch
state. In the illustrated embodiment, the mechanical switch 220 is
in an open position when in the first mechanical switch state and
is in a closed position when in the second mechanical switch state.
In the illustrated embodiment, the solid-state switch 230 is in an
open circuit state when in the first solid-state switch state and
is in a closed circuit state when in the second solid-state switch
state. In the illustrated embodiment, the mechanical switch 220 is
positioned in the second transmission path parallel to the first
transmission path and the solid-state switch 230 is positioned in
the third transmission path parallel to the second transmission
path.
FIG. 7B is a circuit diagram illustrating selected elements of
radio frequency switching circuit 700 while operating in a power
amplifier disabled state, in accordance with the second embodiment.
In this PA disabled state, the power amplifier is decoupled from PA
RF OUT 225.
FIGS. 8A-8D are circuit diagrams each illustrating selected
elements of a respective radio frequency switching circuit
including a mechanical switch and a solid-state switch for
hot-switching immunity and operating in a power amplifier enabled
state, in accordance with third, fourth, fifth, and sixth
embodiments. In this PA enabled state, PA 202 delivers power to RF
PA OUT 225 and any subsequent component(s) in the transmission
path. In the illustrated embodiments, the mechanical switch 220 is
a mechanical relay that serves as the primary switching control for
the RF switching circuit and the solid-state switch 230 is a PIN
diode switch. In other embodiments, the solid-state switch 230 may
be or include another type of solid-state switch, such as a MOSFET,
a bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion. In other embodiments,
the mechanical switch 220 may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
More specifically, RF switching circuit 800 shown in FIG. 8A
couples power amplifier 202 to a subsequent component in a
transmission path that includes power amplifier 202 when operating
in the power amplifier enabled state and decouples power amplifier
202 from the subsequent component when operating in the power
amplifier disabled state. For example, mechanical switch 220 is
configured to couple the output path of power amplifier 202 in a
first transmission path to the subsequent component when in a first
mechanical switch state and to decouple the output path of the
power amplifier from the subsequent component when in a second
mechanical switch state. The solid-state switch 230 is configured
to impart a low impedance at a pin of the mechanical switch 220,
shown as decoupling point 255, to operatively decouple the
mechanical switch 220 from an RF power source when in a first
solid-state switch state and to impart a higher impedance at the
pin of the mechanical switch when in a second solid-state switch
state. The solid-state switch 230 is configured to be in the first
solid-state switch state during transitions of the mechanical
switch 220 from the first mechanical switch state to the second
mechanical switch state and from the second mechanical switch state
to the first mechanical switch state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 210 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and solid-state switch 230. In the
illustrated embodiment, the mechanical switch 220 is in an open
position when in the first mechanical switch state and is in a
closed position when in the second mechanical switch state. In the
illustrated embodiment, the solid-state switch 230 is in an open
circuit state when in the first solid-state switch state and is in
a closed circuit state when in the second solid-state switch state.
In the illustrated embodiment, the mechanical switch 220 is
positioned in a second transmission path parallel to the first
transmission path and the solid-state switch 230 is positioned in a
third transmission path parallel to the second transmission
path.
In another example, RF switching circuit 820 shown in FIG. 8B
couples power amplifier 202 to a subsequent component in a
transmission path that includes power amplifier 202 when operating
in the power amplifier enabled state and decouples power amplifier
202 from the subsequent component when operating in the power
amplifier disabled state. For example, mechanical switch 220 is
configured to couple the output path of power amplifier 202 in a
first transmission path to the subsequent component when in a first
mechanical switch state and to decouple the output path of the
power amplifier from the subsequent component when in a second
mechanical switch state. The solid-state switch 230 is configured
to operatively decouple the mechanical switch 220 from an RF power
source at a pin of the mechanical switch 220, shown as decoupling
point 260, when in a first solid-state switch state but not when in
a second solid-state switch state. In the illustrated embodiment,
rather than imparting a low or high impedance at the mechanical
switch 220, the solid-state switch directly attenuates the RF power
at the decoupling point 260 when in the first solid-state switch
state but does not attenuate the RF power when in the second
solid-state switch state. The solid-state switch 230 is configured
to be in the first solid-state switch state during transitions of
the mechanical switch 220 from the first mechanical switch state to
the second mechanical switch state and from the second mechanical
switch state to the first mechanical switch state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 208 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220. In this
embodiment, solid-state switch 230 is positioned in series with
mechanical switch 220 in the second transmission path. In the
illustrated embodiment, the mechanical switch 220 is in a closed
position when in the first mechanical switch state and is in an
open position when in the second mechanical switch state. In the
illustrated embodiment, the solid-state switch 230 is in an open
circuit state when in the first solid-state switch state and is in
a closed circuit state when in the second solid-state switch
state.
In another example, RF switching circuit 840 shown in FIG. 8C
couples power amplifier 202 to a subsequent component in a
transmission path that includes power amplifier 202 when operating
in the power amplifier enabled state and decouples power amplifier
202 from the subsequent component when operating in the power
amplifier disabled state. For example, mechanical switch 220 is
configured to couple the output path of power amplifier 202 in a
first transmission path to the subsequent component when in a first
mechanical switch state and to decouple the output path of the
power amplifier from the subsequent component when in a second
mechanical switch state. The solid-state switch 230 is configured
to impart a low impedance at a pin of the mechanical switch 220,
shown as decoupling point 265, to operatively decouple the
mechanical switch 220 from an RF power source when in a first
solid-state switch state and to impart a higher impedance at the
pin of the mechanical switch when in a second solid-state switch
state. The solid-state switch 230 is configured to be in the first
solid-state switch state during transitions of the mechanical
switch 220 from the first mechanical switch state to the second
mechanical switch state and from the second mechanical switch state
to the first mechanical switch state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 208 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220. In this
embodiment, solid-state switch 230 is positioned in parallel with
mechanical switch 220. In the illustrated embodiment, the
mechanical switch 220 is in a closed position when in the first
mechanical switch state and is in an open position when in the
second mechanical switch state. In the illustrated embodiment, the
solid-state switch 230 is in an open circuit state when in the
first solid-state switch state and is in a closed circuit state
when in the second solid-state switch state. In the illustrated
embodiment, the mechanical switch 220 is positioned in a second
transmission path parallel to the first transmission path and the
solid-state switch 230 is positioned in a third transmission path
parallel to the second transmission path.
In yet another example, RF switching circuit 860 shown in FIG. 8D
couples power amplifier 202 to a subsequent component in a
transmission path that includes power amplifier 202 when operating
in the power amplifier enabled state and decouples power amplifier
202 from the subsequent component when operating in the power
amplifier disabled state. For example, mechanical switch 220 is
configured to couple the output path of power amplifier 202 in a
first transmission path to the subsequent component when in a first
mechanical switch state and to decouple the output path of the
power amplifier from the subsequent component when in a second
mechanical switch state.
In the illustrated example, the solid-state switch 230 is
configured to impart a low impedance between the mechanical switch
220 and the RF power source of the first transmission path, shown
as decoupling point 270, when in a first solid-state switch state
and to impart a higher impedance at the decoupling point 270 when
in a second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 208 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220 and
transmission cable 207 represents an ideal 90-degree transmission
line in a third transmission path parallel to the second
transmission path between power amplifier 202 and solid-state
switch 230. In the illustrated embodiment, the mechanical switch
220 is in a closed position when in the first mechanical switch
state and is in an open position when in the second mechanical
switch state. In the illustrated embodiment, the solid-state switch
230 is in an open circuit state when in the first solid-state
switch state and is in a closed circuit state when in the second
solid-state switch state.
FIGS. 9A and 9B are circuit diagrams illustrating selected elements
of a radio frequency switching circuit 900 including both a
mechanical switch and a solid-state switch operating in a power
amplifier enabled state and in a power amplifier disabled state,
respectively, in accordance with a seventh embodiment. In the PA
enabled state, PA 202 delivers power to RF PA OUT 225 and any
subsequent component(s) in the transmission path. In the PA
disabled state, PA 202 is decoupled from PA RF OUT 225.
In the illustrated embodiment, the mechanical switch 220 is a
mechanical relay that serves as the primary switching control for
the RF switching circuit and the solid-state switch 230 is a PIN
diode switch. In other embodiments, the solid-state switch 230 may
be or include another type of solid-state switch, such as a MOSFET,
a bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion. In other embodiments,
the mechanical switch 220 may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
The RF switching circuit 900 couples power amplifier 202 to a
subsequent component in a transmission path that includes power
amplifier 202 when operating in the power amplifier enabled state
and decouples power amplifier 202 from the subsequent component
when operating in the power amplifier disabled state. For example,
mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. The solid-state
switch 230 is configured to impart a low impedance at a pin of the
mechanical switch 220, shown as decoupling point 275, to
operatively decouple the mechanical switch 220 from an RF power
source when in a first solid-state switch state and to impart a
higher impedance at the pin of the mechanical switch when in a
second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 914 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and solid-state switch 230. In the
illustrated embodiment, the mechanical switch 230 is positioned in
series with the output path of the power amplifier 202 in the first
transmission path and the solid-state switch 230 is positioned in a
second transmission path parallel to the first transmission path.
In the illustrated embodiment, the solid-state switch 230 is
configured to be in the first solid-state switch state while the
mechanical switch 220 is in the second mechanical switch state and
the solid-state switch 230 is configured to be in the second
solid-state switch state while the mechanical switch 220 is in the
first mechanical switch state. In the illustrated embodiment, the
mechanical switch 220 is in a closed position when in the first
mechanical switch state and is in an open position when in the
second mechanical switch state. In the illustrated embodiment, the
solid-state switch 230 is in an open circuit state when in the
first solid-state switch state and is in a closed circuit state
when in the second solid-state switch state.
FIGS. 10A and 10B are circuit diagrams illustrating selected
elements of a radio frequency switching circuit including both a
mechanical switch and a solid-state switch operating in a power
amplifier enabled state and in a power amplifier disabled state,
respectively, in accordance with an eighth embodiment. In the PA
enabled state, PA 202 delivers power to RF PA OUT 225 and any
subsequent component(s) in the transmission path. In the PA
disabled state, PA 202 is decoupled from PA RF OUT 225.
In the illustrated embodiment, the mechanical switch 220 is a
mechanical relay that serves as the primary switching control for
the RF switching circuit and the solid-state switch 230 is a PIN
diode switch. In other embodiments, the solid-state switch 230 may
be or include another type of solid-state switch, such as a MOSFET,
a bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion. In other embodiments,
the mechanical switch 220 may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay.
The RF switching circuit 1000 couples power amplifier 202 to a
subsequent component in a transmission path that includes power
amplifier 202 when operating in the power amplifier enabled state
and decouples power amplifier 202 from the subsequent component
when operating in the power amplifier disabled state. For example,
mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. The solid-state
switch 230 is configured to impart a low impedance at a pin of the
mechanical switch 220, shown as decoupling point 275, to
operatively decouple the mechanical switch 220 from an RF power
source when in a first solid-state switch state and to impart a
higher impedance at the pin of the mechanical switch when in a
second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 914 represents an
ideal 180-degree transmission line in a second transmission path
between power amplifier 202 and solid-state switch 230. In the
illustrated embodiment, the mechanical switch 220 is positioned in
series with the output path of the power amplifier 202 in the first
transmission path and the solid-state switch 230 is positioned in a
second transmission path parallel to the first transmission path.
In the illustrated embodiment, the solid-state switch 230 is
configured to be in the first solid-state switch state while the
mechanical switch 220 is in the first mechanical switch state and
the solid-state switch 230 is configured to be in the second
solid-state switch state while the mechanical switch 220 is in the
second mechanical switch state. In the illustrated embodiment, the
mechanical switch 220 is in a closed position when in the first
mechanical switch state and is in an open position when in the
second mechanical switch state. In the illustrated embodiment, the
solid-state switch 230 is in a closed circuit state when in the
first solid-state switch state and is in an open circuit state when
in the second solid-state switch state.
In various embodiments, an RF switching circuit that includes both
a mechanical switch and a solid-state switch may be located in
whole or in part within an RF PA module that includes the RF
switching circuit and the power amplifier whose output path is
coupled or decoupled to a subsequent component in a transmission
path based on the state of the RF switching circuit. The RF PA
module may be implemented as a standalone hardware component in the
system integrating the functionality of a power amplifier and a
corresponding RF switching circuit. In other embodiments, the RF
switching circuit may be located entirely outside of the RF PA
module between the power amplifier and an antenna port of a base
station, for example. The location of the RF switching circuit and
the length of the cables coupling the output of the RF switching
circuit to another component may affect the respective states of
the mechanical switch, the solid-state switch, or both, when the RF
switching circuit is operating in the PA enabled state, when the RF
switching circuit is operating in the PA disabled state, and when
the RF switching circuit is transitioning between the PA enabled
state and the PA disabled state.
FIGS. 11A and 11B are circuit diagrams illustrating respective
placements of a radio frequency switching circuit including both a
mechanical switch and a solid-state switch for hot-switching
immunity. For example, in FIG. 11A, the radio frequency switching
circuit is located entirely with an RF PA module 1100 that includes
power amplifier 202 and an RF switching circuit similar to the RF
switching circuit illustrated in FIG. 10A. In this example, there
would be a high impedance at RF PA output 1120 when the RF
switching circuit is in the PA disabled state.
By contrast, in FIG. 11B, a portion of the RF switching circuit
shown in FIG. 10A is located outside of RF PA module 1150. In this
example, there would be a low impedance at output 1130 of RF PA
module 1150 when the RF switching circuit is in the PA disabled
state. However, after an additional 90-degree transmission line,
there would be a high impedance at RF PA output 1120 when the RF
switching circuit is in the PA disabled state. At RF PA output
1120, after this external cable, the high impedance is realized in
the RF network, yielding the desired result of open switch state
when the RF switching circuit is in the PA disabled state. As
illustrated in this example, a desired impedance at the output of
the RF PA module or at the input of a subsequent component in the
transmission path that includes the RF PA module, may be achieved
by the addition of one or more quarter-wave (90-degree) lengths of
cabling, as appropriate.
In some applications of the RF switching circuits described herein,
if an amplifier fails due to a failing power supply, faulty wiring,
or another failure mode in the amplifier, the RF switching circuit
may be put into a state in which power from the rest of the system
is consumed even though the amplifier is disabled. In some
embodiments, to resolve this issue, the RF switching circuits
described herein may include a substitution switch configured to
decouple the output path of a PA from a subsequent component in its
transmission path in the event that no electrical power is supplied
to the solid-state switch. The purpose of the substitution switch
is to impart a low impedance at the solid-state switch connection
point in the event that no electrical power is supplied to the
solid-state switch, but also in the event that, for any other
reason, the solid-state switch cannot be relied upon to decouple
the output path of the PA in a failure mode. While electrical power
is supplied to the solid-state switch, the state of the
substitution switch may have no effect on the operation of the RF
switching circuit. In various embodiments, the substitution switch
may be or include a mechanical switch, such as a mechanical relay
or another type of electromechanically actuated switch having one
or more poles.
In some embodiments, the substitution switch may be controlled
entirely by the power supply such that if, for any reason, the
power supply ceases supplying power to the RF switching circuit or,
more specifically, to the solid-state switch, the substitution
switch will be shorted, putting the RF switching circuit into a
state that is similar to the PA disabled state.
As is the case with the mechanical switches that serve as the
primary switching control for the RF switching circuit, the
configuration of the substitution switch in particular states may
be reversible by adding an odd number of quarter-wave transmission
line segments or a segment whose length is an odd multiple of 90
degrees.
FIGS. 12A and 12B are circuit diagrams illustrating selected
elements of a radio frequency switching circuit 1200 including a
mechanical switch, a solid-state switch, and a substitution switch
operating in a power amplifier enabled state and in a power
amplifier disabled state, respectively, in accordance with a ninth
embodiment. In the PA enabled state, PA 202 delivers power to RF PA
OUT 225 and any subsequent component(s) in the transmission path.
In the PA disabled state, PA 202 is decoupled from PA RF OUT 225
and any subsequent component(s).
In the illustrated embodiment, the mechanical switch 220 is a
mechanical relay that serves as the primary switching control for
the RF switching circuit and the solid-state switch 230 is a PIN
diode switch. In other embodiments, the solid-state switch 230 may
be or include another type of solid-state switch, such as a MOSFET,
a bipolar junction transistor (BJT), or another type of transistor
that can be operated in a switched fashion. In other embodiments,
the mechanical switch 220 may be or include another type of
electromechanically actuated switch having one or more poles,
rather than a mechanical relay. RF switching circuit 1200 has a
topology similar to the topology of RF switching circuit 200
illustrated in FIGS. 2A-2B, 3A, and 5A, with the addition of a
substitution switch 240 that is configured to decouple the output
path of the power amplifier 202 from the subsequent component while
no electrical power is supplied to the solid-state switch 230. Note
that, in other embodiments, a substitution switch may be added to
an RF switching circuit with both a mechanical switch and a
solid-state switch and having a topology other than the topology of
RF switching circuit 200 to decouple the output path of the power
amplifier from the subsequent component while no electrical power
is supplied to the solid-state switch.
The RF switching circuit 1200 couples power amplifier 202 to a
subsequent component in a transmission path that includes power
amplifier 202 when operating in the power amplifier enabled state
and decouples power amplifier 202 from the subsequent component
when operating in the power amplifier disabled state. For example,
mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. The solid-state
switch 230 is configured to impart a low impedance at a pin of the
mechanical switch 220, shown as decoupling point 250, to
operatively decouple the mechanical switch 220 from an RF power
source when in a first solid-state switch state and to impart a
higher impedance at the pin of the mechanical switch when in a
second solid-state switch state. The solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the mechanical switch 220 from the first mechanical
switch state to the second mechanical switch state and from the
second mechanical switch state to the first mechanical switch
state.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 208 represents an
ideal 90-degree transmission line in a second transmission path
between power amplifier 202 and mechanical switch 220, and
transmission cable 210 represents an ideal 90-degree transmission
line in a third transmission path between power amplifier 202 and
solid-state switch 230. In the illustrated embodiment, the
solid-state switch 230 is positioned in a second transmission path
parallel to the first transmission path. The RF switching circuit
1200 also includes a substitution switch 240 in a third
transmission path parallel to the second transmission path that is
configured to decouple the output path of the power amplifier 202
from the subsequent component while no electrical power is supplied
to the solid-state switch 230. As illustrated in FIGS. 12A and 12B,
the substitution switch 240 is an additional mechanical switch, and
more specifically an additional mechanical relay, whose position
when configured to decouple the output path of the power amplifier
202 from the subsequent component is dependent on the length of the
third transmission path. In other embodiments, the substitution
switch may be or include another type of electromechanically
actuated switch having one or more poles, rather than a mechanical
relay. In at least some embodiments, while electrical power is
supplied to the solid-state switch 230, the state of the
substitution switch 240 may have no effect on the operation of the
RF switching circuit and may not be dependent on the state of the
RF switching circuit. For example, the substitution switch 240 may
remain in an OFF state while the RF switching circuit is in the PA
enabled state, while the RF switching circuit is in the PA disabled
state and during transitions of the RF switching circuit from the
PA enabled state to the PA disabled state as long as electrical
power is supplied to the solid-state switch 230.
In the illustrated embodiment, the solid-state switch 230 is
configured to be in the second solid-state switch state while the
mechanical switch 220 is in the first mechanical switch state and
while the mechanical switch is in the second mechanical switch
state. In the illustrated embodiment, the mechanical switch 220 is
in a closed position when in the first mechanical switch state and
is in an open position when in the second mechanical switch state.
In the illustrated embodiment, the solid-state switch 230 is in an
open circuit state when in the first solid-state switch state and
is in a closed circuit state when in the second solid-state switch
state.
FIG. 12C is a circuit diagram illustrating selected elements of a
radio frequency switching circuit 1201 including a mechanical
switch, a solid-state switch, and an intermediate mechanical
switch, in accordance with a tenth embodiment. In the illustrated
embodiment, radio frequency switching circuit 1201 includes
elements similar to those of radio frequency switching circuit 1200
illustrated in FIGS. 12A and 12B. In addition, radio frequency
switching circuit 1201 includes an intermediate mechanical switch,
shown as supplemental relay 290, and an additional transmission
cable 295. In the illustrated embodiment, the solid-state switch
230 enables the intermediate mechanical switch 290 to be safely
hot-switched, which in turn enables the mechanical switch 220 to be
safely hot-switched.
As is the case with radio frequency switching circuit 1200
illustrated in FIGS. 12A and 12B, in the PA enabled state, PA 202
delivers power to RF PA OUT 225 and any subsequent component(s) in
the first transmission path that includes power amplifier 202 and
RF PA OUT 225. In the PA disabled state, PA 202 is decoupled from
PA RF OUT 225 and any subsequent component(s).
In the illustrated embodiment, the mechanical switch 220 and the
intermediate mechanical switch 290 are mechanical relays and the
solid-state switch 230 is a PIN diode switch. In other embodiments,
the solid-state switch 230 may be or include another type of
solid-state switch, such as a MOSFET, a bipolar junction transistor
(BJT), or another type of transistor that can be operated in a
switched fashion. In other embodiments, either or both of the
mechanical switch 220 and the intermediate mechanical switch 290
may be or include another type of electromechanically actuated
switch having one or more poles, rather than a mechanical
relay.
In the illustrated embodiment, transmission cable 206 represents an
ideal 90-degree transmission line in the first transmission path
between power amplifier 202 and the output of RF switching circuit
200, shown as RF PA OUT 225. Transmission cable 208 represents an
ideal 90-degree transmission line in a third transmission path
between power amplifier 202 and intermediate mechanical switch 290,
transmission cable 295 represents an ideal 90-degree transmission
line in a fourth transmission path between power amplifier 202 and
solid-state switch 230. In the illustrated embodiment, the
intermediate mechanical switch 290 is positioned in the third
transmission path and the solid-state switch 230 is positioned in
the fourth transmission path parallel to the third transmission
path. This embodiment additionally may be configured to operatively
decouple the output path of the power amplifier 202 from the
subsequent component while no electrical power is supplied to the
solid-state switch 230.
In the illustrated embodiment, the mechanical switch 220 serves as
the primary switching control for the RF switching circuit, the
solid-state switch 230 is configured to affect the intermediate
mechanical switch 290 directly, and the intermediate mechanical
switch 290 is configured to protect the mechanical switch 220
during transitions of the state of the mechanical switch 220.
Mechanical switch 220 is configured to couple the output path of
power amplifier 202 in a first transmission path to the subsequent
component when in a first mechanical switch state and to decouple
the output path of the power amplifier from the subsequent
component when in a second mechanical switch state. However, unlike
in radio frequency switching circuit 1200 illustrated in FIGS. 12A
and 12B, the solid-state switch 230 is configured to impart a low
impedance at a pin of the intermediate mechanical switch 290, shown
as decoupling point 285, rather than at a pin of the mechanical
switch 220, when in a first solid-state switch state and to impart
a higher impedance at the pin of the intermediate mechanical switch
290 when in a second solid-state switch state.
When the solid-state switch 230 is in the second solid-state switch
state, the state of the intermediate mechanical switch 290 affects
the impedance at a pin of mechanical switch 220, shown as
decoupling point 280. For example, the solid-state switch 230 is
configured to be in the first solid-state switch state during
transitions of the intermediate mechanical switch 290 from the
first mechanical switch state to the second mechanical switch state
and from the second mechanical switch state to the first mechanical
switch state. When the solid-state switch 230 is in the second
solid-state switch state and the intermediate mechanical switch 290
is in an OFF state, a low impedance is imparted at the decoupling
point 280, operatively decoupling the mechanical switch 220 from an
RF power source in the second transmission path between power
amplifier 202 and mechanical switch 220.
In at least some embodiments, during a switching operation using
the RF switching circuit 1201 shown in FIG. 12C, the order of the
operations may be as follows: 1) the solid-state switch shown as
PIN diode 230 is transitioned to its OFF state, thus shorting the
intermediate mechanical switch shown as supplemental relay 290; 2)
the supplemental relay 290 is transitioned to its OFF state; 3) the
PIN diode 230 is transitioned to its ON state, thereby presenting a
high impedance at 285 at the intermediate mechanical switch, which
along with the high impedance presented by the intermediate
mechanical switch itself at 285, creates a composite high
impedance, thereby shorting 280 and operatively decoupling RF power
to the mechanical switch shown as main relay 220; 4) the main relay
220 is transitioned from its current state to the opposite state
(e.g., from its ON state to its OFF, or vice versa); 5) the PIN
diode 230 is transitioned to its OFF state; 6) the supplemental
relay 290 is returned to its ON state; and 7) the PIN diode 230 is
returned to its ON state.
The example RF switching circuit illustrated in FIG. 12C may have
an overall performance substantially similar to the performance of
the RF switching circuits illustrated in FIGS. 2A, 2B, 3A, 5A, 7A,
7B, 12A and 12B, but may incur additional costs due to the
inclusion of an additional mechanical switch.
FIG. 13 is a block diagram illustrating selected elements of a
system 1300 including one or more a radio frequency switching
circuits, each including a mechanical switch and a solid-state
switch for hot-switching immunity, in accordance with some
embodiments. The illustrated components of FIG. 13, along with
other various modules and components, may be coupled to each other
by or through one or more control or data buses that enable
communication between them. The use of control and data buses for
the interconnection between and exchange of information among the
various modules and components would be apparent to a person
skilled in the art in view of the description provided herein. In
various embodiments, system 1300 may be, or be a component of, a
base station, a mobile station, or another device configured to
transmit and, in some cases, receive radio frequency signals. In
some embodiments, system 1300 may be integrated with an electronic
communications device, for example, a portable radio, a cellular
telephone, a tablet computer, and the like.
In the illustrated embodiment, system 1300 includes a front end
1305, a transceiver 1310, an encoder/decoder 1320, a
modulator/demodulator 1315, one or more filters 1325, a processing
unit 1330, which includes memory 1335, one or more user input
mechanisms 1340, one or more input/output device interfaces 1350, a
network interface 1355, and a display 1345. In other embodiments,
system 1300 may include more, fewer, or different elements than
those illustrated in FIG. 13.
The front end 1305 may include various digital and analog
components, some of which, for brevity, are not described herein.
In various embodiments, these digital and analog components may be
implemented in hardware, software, or a combination of both, and
may include one or more radio frequency filters, one or more signal
splitters 1308, one or more signal combines 1309, radio frequency
switching circuits 1307, power amplifiers 1306, and the like. The
front end 1305 may include one or more wired or wireless
input/output (I/O) interfaces configurable to communicate with base
stations, mobile stations, or other devices configured to transmit
and, in some cases, receive radio frequency signals, including
radio frequency signals generated through the conversion of
baseband signals. In at least some embodiments, the front end 1305
may receive radio frequency signals from an antenna communicatively
coupled to the front end 1305 (not shown), optionally filter the
signals using one or more radio frequency filters, and pass them to
the transceiver 1310. Likewise, the front end 1305 may receive
radio frequency signals from the transceiver 1310, optionally
filter the signals using one or more radio frequency filters, pass
the signals through one or more power amplifiers 1306 and
corresponding RF switching circuits 1307, as described herein, and
transmit them via the antenna. In some embodiments, system 1300 may
include multiple power amplifiers 1306 and RF switching circuits
1307 in respective parallel paths and may include multiple
splitter/combiner pairs 1308/1309 to route the signals, or portions
thereof, to each of the parallel paths.
In various embodiments, transceiver 1310 may be or include a
wireless transceiver such as a DMR transceiver, a P25 transceiver,
a Bluetooth transceiver, a Wi-Fi transceiver perhaps operating in
accordance with an IEEE 802.11 standard, such as 802.11a, 802.11b,
or 802.11g, a WiMAX transceiver perhaps operating in accordance
with an IEEE 802.16 standard, an LTE transceiver, or another
similar type of wireless transceiver configurable to communicate
via a wireless radio network. In some embodiments, transceiver 1310
may be or include one or more wireline transceivers 1310, such as
an Ethernet transceiver, a Universal Serial Bus (USB) transceiver,
or similar transceiver configurable to communicate via a twisted
pair wire, a coaxial cable, a fiber-optic link or a similar
physical connection to a wireline network. In various embodiments,
transceiver 1310 may be or include a software defined transceiver
implemented using a frequency and modulation-agile Software Defined
Radio (SDR) technology. The transceiver 1310 may be coupled to
combined modulator/demodulator 1315, which is coupled to
encoder/decoder 1320.
In the illustrated embodiment, the transceiver 1310 receives
modulated radio frequency signals, e.g., a carrier frequency signal
modulated with a baseband signal, from an antenna via the front end
1305. The radio frequency signals may be modulated using any of a
variety of modulation types and formats, in different embodiments
and at different times. Modulator/demodulator 1315 extracts and
demodulates the in-phase and quadrature baseband signals from the
received modulated radiofrequency signal. The transceiver 1310 may
communicate the demodulated baseband signals to encoder/decoder
1320, which decodes the signals to extract data encoded in the
signals. Modulator/demodulator 1315 may receive a baseband signal
encoded with data by encoder/decoder 1320 and modulate the baseband
signal with a carrier signal to produce a modulated radio frequency
signal. The transceiver 1310 transmits the modulated radio
frequency signal via the front end 1305 and the antenna.
The processing unit 1330 may include a microprocessor, a graphics
processing unit (GPU), a microcontroller, a system-on-chip, a
field-programmable gate array, a programmable mixed-signal array,
or, in general, any system or sub-system that includes nominal
memory and that is capable of executing a sequence of instructions
in order to control hardware including, for example, program
instructions that control one or more RF switching circuits 1307,
as described herein. In various embodiments, memory 1335 may
include a Read Only Memory (ROM) and a Random Access Memory (RAM)
for storing, at various times, program instructions and data for
performing some or all of the methods described herein for
controlling RF switching circuits that include both a mechanical
switch and a solid-state switch for hot-switching immunity. For
example, in various embodiments, any or all of the operations of
method 100 illustrated in FIG. 1, method 400 illustrated in FIG. 4,
or method 600 illustrated in FIG. 6 may be performed by program
instructions executing on processing unit 1330.
Other program instructions, when executed by the processing unit
1330, may perform other functions of system 1300, such as other
functionality features of a base station, mobile station, or other
device configured to transmit and, in some cases, receive radio
frequency signals. For example, in some embodiments, memory 1335
may also store program instructions and data for initializing
system components, encoding and decoding voice, data, control, or
other signals that may be transmitted or received between system
1300 and one or more base stations or mobile stations (not shown).
In some embodiments, some or all of the functionality of
encoder/decoder 1320 or of other elements of system 1300 shown in
FIG. 13 may be implemented by program instructions executed by
processing unit 1330 or another processing unit (not shown). In
some embodiments, some or all of the functionality of filters 1325
may be implemented by program instructions executed by processing
unit 1330 or another processing unit (not shown).
User input mechanisms 1340 may include any of a variety of suitable
mechanisms for receiving user input, such as for initiating a
change in the state of an RF switching circuit 1307, as described
herein. User input may be provided via, for example, a keyboard or
keypad, a microphone, soft keys, icons, or soft buttons on a touch
screen of a display, such as display 1345, a scroll ball, a mouse,
buttons, and the like.
In this example embodiment, input/output device interfaces 1350 may
include one or more analog input interfaces, such as one or more
analog-to-digital (A/D) convertors, or digital interfaces for
receiving signals or data from, and sending signals or data to, one
or more input/output devices. In some embodiments, input/output
device interfaces 1350 may include a graphical user interface (GUI)
generated, for example, by processing unit 1330 from program
instructions and program data in memory 1335 and presented on
display 1345, enabling a user to interact with display 1345. In
some embodiments, input/output device interfaces 1350 may include
one or more analog input interfaces for receiving baseband or radio
frequency signals. In some embodiments, input/output device
interfaces 1350 may include one or more external memory interfaces
through which processing unit 1300 may be coupled to an external
memory (not shown in FIG. 13). Such an external memory may include,
for example, a hard-disk drive (HDD), an optical disk drive such as
a compact disk (CD) drive or digital versatile disk (DVD) drive, a
solid-state drive (SSD), a tape drive, a flash memory drive, or a
tape drive, to name a few. In various embodiments, or at certain
times, program data or program instructions may reside in external
memory rather than, or in addition to, within memory 1335.
Display 1345 may include any suitable display technology for
presenting information to a user including, for example, the state
of an RF switching circuit. Each of the user input mechanisms 1340
and display 1345 may be communicatively coupled to the processing
unit 1330.
Network interface 1355 may be a suitable system, apparatus, or
device operable to serve as an interface between processing unit
1330 and a network. Network interface 1355 may enable processing
unit 1330 to communicate over a network using a suitable
transmission protocol or standard, including, but not limited to,
transmission protocols and standards enumerated below with respect
to the discussion of the network. In some embodiments, network
interface 1355 may be communicatively coupled via a network to a
network storage resource. The network may be implemented as, or may
be a part of, a storage area network (SAN), personal area network
(PAN), local area network (LAN), a metropolitan area network (MAN),
a wide area network (WAN), a wireless local area network (WLAN), a
virtual private network (VPN), an intranet, the Internet or another
appropriate architecture or system that facilitates the
communication of signals, data or messages, which are generally
referred to as data. The network may transmit data using a desired
storage or communication protocol, including, but not limited to,
Fibre Channel, Frame Relay, Asynchronous Transfer Mode (ATM),
Internet protocol (IP), other packet-based protocol, small computer
system interface (SCSI), Internet SCSI (iSCSI), Serial Attached
SCSI (SAS) or another transport that operates with the SCSI
protocol, advanced technology attachment (ATA), serial ATA (SATA),
advanced technology attachment packet interface (ATAPI), serial
storage architecture (SSA), integrated drive electronics (IDE), or
any combination thereof. The network and its various components may
be implemented using hardware, software, or any combination
thereof.
Network interface 1355 may enable wired or wireless communications
to and from processing unit 700 and other elements of a base
station, mobile station, or other device. In some embodiments,
baseband or radio frequency signals may be received over network
interface 1355 rather than one of input/output device interfaces
1350.
FIG. 14 is a block diagram illustrating selected elements of a
transmission path in an electronic communication device including
parallel power amplifiers and corresponding parallel radio
frequency switching circuits, one or more of which may include a
mechanical switch and a solid-state switch for hot-switching
immunity, in accordance with some embodiments. For example, in some
embodiments that include parallel power amplifiers, not all of the
power amplifiers can be hot-switched. In such embodiments, RF
switching circuits such as those described herein may only be
coupled to those power amplifiers that can be hot-switched. In the
illustrated embodiment the transmission path may represent a
transmission path in a base station whose output is coupled to an
antenna when operating in the PA enabled mode. In the illustrated
example, the transmission path includes an N-way splitter 1422, N
parallel RF PA branches, each including an RF switching circuit,
and an N-way combiner 1424. In at least some embodiments, the
impedance of the splitter 1422 and combiner 1424 may be optimized
for two- and three-way operation. In other embodiments, the
splitter 1422 and combiner 1424 may be configured to operate in an
electronic device having a different number of parallel RF BA
branches. In at least some embodiments, it may be possible to
remove or disable one RF PA branch without incurring extra
insertion loss, thereby maintaining the same gain as for the full
N-way circuit.
In the illustrated embodiment, there is a switch at the input of
each RF PA module. If one of the RF PA modules is removed or
otherwise disconnected, the corresponding branch will present an
open circuit at the connection points at its input and at its
output. The same applies if the RF switch at the input of an RF PA
module is open. At the output of an RF PA module that is disabled,
the RF switch may be exposed to the RF power of the other RF PA
modules. The output may therefore be exposed to hot-switching of
high RF power. In the illustrated example, the electronic device
may have a requirement for optimal IMD performance in both the PA
enabled state and the PA disabled state. In at least some
embodiments, the techniques described herein for providing an RF
switching circuit with both a mechanical switch and a solid-state
switch for hot-switching immunity may also allow the IMD
performance requirements to be met.
In at least some embodiments, the transmission path includes a
baseband input signal interface 1402, an encoder 1404, a modulator
1406, and an up-converter 1408, the output of which is an input
1410 to the parallel RF PA branches 1416, and an antenna 1425. Each
of the RF PA modules 1416 includes a respective power amplifier
that is coupled to or decoupled from a cable at its output
dependent on the state of a corresponding RF switching circuit.
Each RF switching circuit may be or include an RF circuit with both
a mechanical switch and a solid-state switch in any of the
topologies described herein or any other topology in which the
mechanical switch serves as the primary switching control for the
RF switching circuit and the solid-state switch is configured to
decouple a pin of the mechanical switch from an RF power source
during transitions of the state of the mechanical switch. The
outputs of the RF switching circuits are coupled to N-way combiner
1424 using respective cables (not shown in FIG. 13). In one
example, the N-way combiner may include cables representing ideal
90-degree transmission lines carrying signals that are combined to
provide an output signal to antenna 1425.
In embodiments in which the RF switching circuits within RF PA
modules 1416 include a substitution switch, as described above in
reference to FIGS. 12A-12C, the RF PA may maintain a high impedance
output state with or without the presence of locally-suppled
electrical power. This substitution switch may be critical to
maintaining isolation of the N-way combiner during a RF PA module
power failure while maintaining regulatory emission limits.
Described herein are high power RF switching circuits that include
a combination of a mechanical switch, such as a mechanical relay,
and a solid-state switch, such as a PIN diode, with a particular
sequencing of these elements to provide IMD performance and
hot-switching capability that are superior to existing RF switching
solutions. As noted above, the mechanical switch may reduce thermal
stress on the solid-state switch during steady-state operation and
may reduce or eliminate IMD that would otherwise be caused by the
solid-state switch. The solid-state switch may reduce hot-switching
stress on the mechanical switch during transitions from an open
circuit condition to a short circuit condition or from a short
circuit condition to an open circuit condition. A substitution
switch maintains an open circuit impedance with or without locally
supplied electrical power.
The use of the techniques described herein may allow systems and
devices to meet requirements for ultra-reliable high-power RF
hot-switching with low IMD at a modest cost in certain
applications, such as in power amplifiers and RF communication
system base stations. For example, in various embodiments, these
techniques may provide a robust RF switching circuit that is immune
to hot-switching with greater than 100 W RMS and greater than 1 KW
peak RF power, that has high IMD performance, such as lower than
-80 dBc, that has a very low cost compared to existing mechanical
relays that are designed to handle high levels of hot-switching,
that has high reliability, such as greater than 20 k cycles in one
embodiment, and that provides high impedance output and high IMD
performance with and without an available DC power supply control.
In addition, because it is not necessary to use large mechanical
relays with slow switching times that are inconsistent over
temperature, the RF switching circuits described herein may have
significant advantages over existing solutions, both in terms of
absolute throwing time and variations in throwing time, making them
particularly attractive for use in radio applications in which
size, current drain, and temperature are important
considerations.
In the foregoing specification, specific embodiments have been
described. However, one of ordinary skill in the art appreciates
that various modifications and changes can be made without
departing from the scope of the invention as set forth in the
claims below. Accordingly, the specification and figures are to be
regarded in an illustrative rather than a restrictive sense, and
all such modifications are intended to be included within the scope
of present teachings.
The benefits, advantages, solutions to problems, and any element(s)
that may cause any benefit, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential features or elements of any or all the
claims. The invention is defined solely by the appended claims
including any amendments made during the pendency of this
application and all equivalents of those claims as issued.
Moreover, in this document, relational terms such as first and
second, top and bottom, and the like may be used solely to
distinguish one entity or action from another entity or action
without necessarily requiring or implying any actual such
relationship or order between such entities or actions. The terms
"comprises," "comprising," "has", "having," "includes",
"including," "contains", "containing" or any other variation
thereof, are intended to cover a non-exclusive inclusion, such that
a process, method, article, or apparatus that comprises, has,
includes, contains a list of elements does not include only those
elements but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. An element
proceeded by "comprises . . . a", "has . . . a", "includes . . .
a", "contains . . . a" does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises, has, includes,
contains the element. The terms "a" and "an" are defined as one or
more unless explicitly stated otherwise herein. The terms
"substantially", "essentially", "approximately", "about" or any
other version thereof, are defined as being close to as understood
by one of ordinary skill in the art, and in one non-limiting
embodiment the term is defined to be within 10%, in another
embodiment within 5%, in another embodiment within 1% and in
another embodiment within 0.5%. The term "coupled" as used herein
is defined as connected, although not necessarily directly and not
necessarily mechanically. A device or structure that is
"configured" in a certain way is configured in at least that way,
but may also be configured in ways that are not listed.
It will be appreciated that some embodiments may be comprised of
one or more generic or specialized processors, or "processing
devices", such as microprocessors, digital signal processors, GPUs,
customized processors and field programmable gate arrays (FPGAs)
and unique stored program instructions, including both software and
firmware, that control the one or more processors to implement, in
conjunction with certain non-processor circuits, some, most, or all
of the functions of the method or apparatus described herein.
Alternatively, some or all functions could be implemented by a
state machine that has no stored program instructions, or in one or
more application specific integrated circuits (ASICs), in which
each function or some combinations of certain of the functions are
implemented as custom logic. Of course, a combination of the two
approaches could be used.
Moreover, an embodiment can be implemented as a computer-readable
storage medium having computer readable code stored thereon for
programming a computer including for example, a processor, to
perform a method as described and claimed herein. Examples of such
computer-readable storage mediums include, but are not limited to,
a hard disk, a CD-ROM, an optical storage device, a magnetic
storage device, a ROM (Read Only Memory), a PROM (Programmable Read
Only Memory), an EPROM (Erasable Programmable Read Only Memory), an
EEPROM (Electrically Erasable Programmable Read Only Memory) and a
Flash memory. Further, it is expected that one of ordinary skill,
notwithstanding possibly significant effort and many design choices
motivated by, for example, available time, current technology, and
economic considerations, when guided by the concepts and principles
disclosed herein will be readily capable of generating such
software instructions and programs and ICs with minimal
experimentation.
The Abstract of the Disclosure is provided to allow the reader to
quickly ascertain the nature of the technical disclosure. It is
submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features are grouped together in various embodiments for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus, the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separately claimed subject matter.
* * * * *